1. Field of the Invention
The present invention relates to an ink especially suitable for use in ink-jet printers, and more particularly, to an ink suitable for use in conduct recording by flying the ink out of an orifice of a recording head by the action of thermal energy, an ink-jet recording method and instruments making use of such an ink.
The present invention also relates to an ink excellent in ejection stability and a production method thereof.
This invention further relates to a method of stabilizing the fly of ink droplets.
2. Related Background Art
An ink-jet recording method is a recording method in which recording is conducted by forming flying droplets of an ink by one of various systems and applying the droplets to a recording material such as paper.
An ink-jet recording apparatus in which this kind of recording method is adopted can conduct high-speed printing and high-density recording with low noises. In addition, the apparatus itself can be miniaturized because treatments such as development and fixing are unnecessary to plain paper, and is good in productivity upon mass production and produced inexpensively. Therefore, such an apparatus has attracted special attention.
In particular, an On-Demand type ink-jet recording apparatus does not require a high-voltage generating device and a useless-ink recovering device, which are said to be necessary to a continuous type ink-jet recording apparatus, and hence can be miniaturized. Therefore, its application is promising.
In particular, an ink-jet recording apparatus making use of an ink-jet recording head described in Japanese Patent Publication No. 61-59914, in which a part of a liquid flow path filled with a liquid is heated to cause the liquid to undergo pressure change attendant on volume increase by rapid bubbling, thereby forming flying droplets of the liquid to be ejected from an orifice communicating with the liquid flow path, and the droplets are than applied to a recording material to make a record thereon, has attracted attention because it has such advantages that since formation of a high-density multi-orifice in the ink-jet recording head can be realized with ease, printing speed can be enhanced by making the head longer, and high-quality images can be provided.
In the ink-jet recording head making good use of thermal energy for forming the flying droplets, a means for heating an ink generally is equipped with an electrothermal converter comprising a heating resistor capable of generating heat by applying an electric signal to heat the ink and an electrode for applying the electric signal to the heating resistor (hereinafter may referred to as heater).
The heater and electrode are formed by using a semiconductor process. For example, a wiring (electrode) formed of a metal (for example, Al, Au, Ag, Cu or the like), which is an electric conductor, is laminated on a heating resistor (made of a heat-resistant resistor material such as HfB.sub.2, ZrB.sub.2, TaN.sub.2 or TaSi) provided on a base (for example, Si, glass, ceramic or the like) in such a manner that portions of the intermediate layer are exposed, thereby forming the heater and electrode. Namely, the exposed portions of the intermediate layer serve as a heater. In order to prevent electrolytic corrosion and oxidation by the ink, a protective film excellent in heat resistance and ink-barrier properties, or the like is further provided on at least the heater and the electrode as needed.
In the ink-jet recording method in which the heater is energized repeatedly by electric signals according to recording signals to generate heat at a high temperature, thereby heating the ink to eject droplets of the ink, the evenness of the ejection volume and ejection velocity of the ink droplets ejected according to the recording signals, i.e., the stability of recording properties of the ejected droplets, is related to the stability of image quality at a high level upon recording even under any conditions (for example, high frequency). Therefore, developments have heretofore been conducted paying attention to how to always stabilize the recording properties of an ink droplet ejected according to every recording signal even under any conditions to permit keeping the quality of recorded images at a high level.
In order to always stabilize the recording properties of the ink droplet ejected according to every recording signal to keep the quality of recorded images at a high level, it is necessary to always keep the size and shape of a bubble generated on the heater according to every recording signal uniform.
However, it has been very difficult to always keep the size and shape of the bubble generated on the heater according to every recording signal uniform even under any conditions. It has been almost impossible to achieve this by the conventional inks.